Measurement of the intensity of the terrestrial magnetic field and that of its transitory variations has had practical application for some time, especially in geophysical prospecting (mineral or petroleum). This is true also of measurements of the north-south, east-west and vertical components of the terrestrial magnetic field.
Such measurements made on the ocean floor offer wide perspectives, for example, for the exploitation of the continental plateau, but such an application introduces more practical difficulties than for a similar measurement on land.
The measurement of the total intensity, commonly denoted F, of the magnetic field is relatively easy to effect with nuclear resonance or optical pumping magnetometers, which are practically insensitive to the direction of the probe. The situation is quite different in the measurement of horizontal components which previously has required a precise orientation of the sensor in a given direction. As example, U.S. Pat. No. 3,508,142 describes a magnetometer for measurement of variations of the east-west component, commonly denoted D, on the ocean bottom. The applicant in the above mentioned U.S. patent also described this magnetometer in the article by J. H. Filloux entitled "An Ocean Bottom D Component Magnetometer" which appeared in the U.S. journal Geophysics, vol. 32, no. 6, December 1967. However, this magnetometer does not provide for measurements of the north-south component, commonly denoted H.